In shopping malls, office buildings, apartment buildings, and other properties having multiple occupants, it is common to provide a plurality of trash compactors of a type comprising a trash container, a hydraulic ram operative in compacting strokes for compacting trash within the container, and a hydraulic pump operative for advancing and retracting the ram in such manner that hydraulic pressure is capable of being sensed between the pump and the ram. Frequently, arrangements are made for a hauler to empty the containers of specific ones of the trash compactors on a periodic basis, or whenever the hauler is contacted by a manager. Commonly, the hauler charges similar hauling fees whether the containers are filled partially or completely. There is a need, therefore, for managers of such properties to receive current information concerning which of the trash compactors require and do not require emptying.
As exemplified in Clar U.S. Pat. No. 3,336,861, Clar U.S. Pat. No. 3,534,678, Woyden U.S. Pat. No. 3,636,863, and Brown U.S. Pat. No. 4,603,625, it is known to provide a trash compactor with pressure-sensing or other means for determining when the container of the trash compactor is full. The Woyden patent discloses an arrangement of such means wherein telephone lines are used to send an alarm signal to a central office when an abnormal condition is sensed. Various systems have been disclosed for monitoring a plurality of trash compactors of the type noted above from a central location.
An early example of such a system is disclosed in Budoff U.S. Pat. No. 4,044,664. In that system, each trash compactor has a detector including a pressure switch for detecting increased pressure in the hydraulic fluid driving a hydraulic ram in such trash compactor when the container of such trash compactor has become packed. Moreover, when the container of a trash compactor becomes packed, a station selector at a central location deactivates the trash container and activates a trash compactor having an empty container.
Another such system sold and used heretofore includes compactor controllers manufactured by Petro-Vend, Inc., for Waste Management, Inc. In that system, a compactor controller including a microprocessor at each trash compactor is arranged for limiting access to authorized users, for monitoring usage of such trash compactor by each authorized user and by all authorized users, for recording data concerning such usage, and for transmitting data concerning such usage to a computer at a central location, via a modem and telephone connections.
Various embodiments of such a system are disclosed in Neumann et al. U.S. Pat. No. 5,016,197. In each embodiment, a sensing unit associated with each trash compactor transmits data to a computer at a central location, via telephone lines. The computer determines fullness of each trash compactor from the transmitted data. In one embodiment, the transmitted data include data relating to instantaneous pressures and to actuation of a limit switch. In another embodiment, the transmitted data include sequences of instantaneous pressure data, from which the computer compiles a database for each trash compactor. The computer determines fullness from the database. In other embodiments, the transmitted data include data relating to ram work, changes in pump motor current, or increases in container weight.